This invention is in the field of Venetian blind window coverings and in particular such blinds with two separate tiers of slats.
It is well known to provide a venetian blind with separate upper and lower tiers of slats which can be tilted independently of each other. These two-tier blinds require a mechanism for tilting the tiers independently. Examples of such mechanisms are disclosed in U.S. Pat. No. 4,621,672 to Hsu, U.S. Pat. No. 4,869,308 to Chang, U.S. Pat. No. 5,119,868 to Werner, U.S. Pat. No. 5,845,691 to Gaines, and U.S. Pat. No. 6,076,587 to Pastor.
The Hsu mechanism uses two worm wheels driven by first and second worms. The worms have a splined inner aperture. A gear is mounted on a shaft. The shaft is moved along its axis so that the gear moves from engaging the first worm to tilt a first tier, to engaging the second worm to tilt a second tier of slats.
The Chang mechanism uses a gear fixed to each of the two tilting shafts, and an outer sleeve with an inner splined portion that is moved so that the splined portion engages and drives one or the other of the gears.
The Werner mechanism utilizes a pair of outer sleeves at each side of the blind, one of each pair tilting the upper tier, and the other of the pair tilting the lower tier. Two gears are fixed to a shaft which slides so that the gears engage one or the other sleeve at each end, or both in order to operate the tiers together.
The Gaines mechanism uses two separate control rods, one to tilt the upper tier and one to tilt the lower tier.
The Pastor mechanism employs a reversing mechanism with plates meshing and un-meshing in response to a bias force. The tiers tilt together until over-rotation causes the plates to un-mesh, and one tier then moves in the opposite direction.
While the above mechanisms are suitable for the purpose, an improved economical and simple mechanism requiring only one control rod, which could be easily moved intuitively to the proper position for adjusting the desired tier of slats, would be beneficial.
It is the object of the present invention to provide a simple and economical apparatus for tilting upper and lower tiers of slats in a venetian blind independently.
It is a further object of the present invention to provide such an apparatus that utilizes a single driving member to drive one or the other of a pair of shafts, each shaft controlling one of the upper and lower tiers of slats, wherein the driving member moves pivotally from engagement with one shaft to engagement with the other shaft.
In a first aspect the invention provides an apparatus for tilting upper and lower tiers of slats in a venetian blind independently. The apparatus comprises a headrail attached to a top end of the venetian blind. A first shaft is rotatably mounted in the headrail and is operatively connected to the upper tier of slats and is operative to tilt the upper tier of slats when rotated. A second shaft is rotatably mounted in the headrail substantially parallel to the first shaft. The second shaft is operatively connected to the lower tier of slats and is operative to tilt the lower tier of slats when rotated. A first worm wheel is attached to the first shaft such that a shaft axis and wheel axis thereof coincide, the first worm wheel rotating with the first shaft. A second worm wheel is attached to the second shaft such that a shaft axis and wheel axis thereof coincide, the second worm wheel rotating with the second shaft. The second worm wheel is located on the second shaft at a horizontal location substantially vertically aligned with the first worm wheel. A worm is pivotally mounted in the headrail about a substantially horizontal axis, the worm movable about the horizontal axis from a first position engaging the first worm wheel and disengaged from the second worm wheel, to a second position engaging the second worm wheel and disengaged from the first worm wheel. The worm is rotatable about a worm axis such that rotation of the worm causes rotation of the engaged worm wheel and the respective shaft. A control rod is operatively connected to the worm to rotate the worm, and is further operative to move the worm from the first position to the second position.
In a second aspect the invention provides an apparatus for tilting upper and lower tiers of slats in a venetian blind independently. The apparatus comprises a headrail attached to a top end of the venetian blind. A first shaft is rotatably mounted in the headrail and is operatively connected to the upper tier of slats and is operative to tilt the upper tier of slats when rotated. A second shaft is rotatably mounted in the headrail substantially parallel to the first shaft. The second shaft is operatively connected to the lower tier of slats and is operative to tilt the lower tier of slats when rotated. A driving member is pivotally mounted in the headrail and is movable from a first position engaging the first shaft and disengaged from the second shaft, to a second position engaging the second shaft and disengaged from the first shaft. The driving member is rotatable about an axis hereof such that rotation of the driving member causes rotation of the engaged shaft. A control rod is operatively connected to the driving member to rotate the driving member, and is further operative to move the driving member from the first position to the second position.